1. Field of the Invention
This invention relates generally to large-scale embroidery machines, and more particularly to cutting and gripping apparatus that facilitates positive cutting of all threads so that the embroidery operation can be quickly resumed.
2. Description of the Related Art
On large-scale embroidery machines with several hundred embroidery positions, it is difficult to cut and secure the embroidery yarn by hand, which thus causes prolonged down times. Furthermore, the embroidery yarn on the front side should be cut cleanly and as close to the bottom of the embroidery as possible in order to save on the additional cutting process. Such a cutting and nipping device also offers great advantages in programming and embroidering colored patterns or repeat patterns. Cutting and nipping devices developed for sewing machines or multi-head embroidery machines cannot be adapted. They are too large for the standard needle spacing of 27.01 mm (1 French inch) and they are too complicated and expensive for use on hundreds of embroidery positions. Examples of relevant but different structures are discussed below.
Swiss patent 577,587 (Pfaff) discloses such a device consisting of multi-head embroidery machines for nipping and cutting the needle thread. With 500 to 1000 embroidery positions on a large-scale embroidery machine with a spacing of 27.01 mm, such a device is hardly feasible from the standpoint of either size or cost.
Swiss patent 536,893 (Metalmeccanica) describes a cutting device for the front threads on a large-scale embroidery machine. A blade is mounted on a carriage which is moved over the entire length of the machine in parallel with the plane of the fabric, so the front threads are cut one after the other. A clean cut can be achieved only if the front threads are stretched taut. Hundreds of threads must be cut by the same blade with each cutting operation, which thus cause the blade to quickly become dull. When performing a cut with this device, there is a side force acting on the thread at the moment of cutting, which can lead to a defect in the resulting knit due to the pulling effect. Gripping or nipping of the thread is impossible with this type of device. A cutting device that does not include a means of gripping the thread cannot be used with an embroidery machine because most of the threads would slip out of the needles in a short period of time.
Swiss patent 647,283 (Heinzle) discloses a simple cutting and gripping device that can be attached to the pressure foot provided with each needle. Reliable cutting of the threads cannot be expected due to the relatively slow lateral movement of the embroidery frame. Eventually, loosening or destruction of the cutting and gripping elements can be expected due to the repeated impacts of the pressure foot against the fabric during the embroidery operation.
German patent 3,502,886 (Reich) discloses cutting elements mounted on a shaft. The cutting elements are pressed against the fabric and thus advanced on the fabric by the revolutions of this shaft. In this forward movement, the threads are to be cut by a single blade. No device is provided for gripping the thread.